Which of the following is the weakest reducing agent?

For the cell reaction $Mg_{(s)} + Zn^{2+}_{(aq)} (1M) \rightarrow Zn_{(s)} + Mg^{2+}_{(aq)} (1M)$,the $emf$ is $1.60 \ V$. The $E$ of the cell is ........ $V$.

Given are $E^o$ values for some half reactions:
$I_2 + 2e^- \to 2I^{-}; E^o = 0.54 \ V$
$MnO_4^- + 8H^{+} + 5e^- \to Mn^{2+} + 4H_2O; E^o = 1.52 \ V$
$Fe^{3+} + e^- \to Fe^{2+}; E^o = 0.77 \ V$
$Sn^{4+} + 2e^- \to Sn^{2+}; E^o = 0.1 \ V$
The strongest reducant and oxidant respectively are:

Aluminium displaces hydrogen from acids but copper does not. $A$ galvanic cell prepared by combining $Cu/Cu^{2+}$ and $Al/Al^{3+}$ has an e.m.f. of $2.0 \ V$ at $298 \ K$. If the potential of copper electrode is $+0.34 \ V$,that of aluminium is .......... $V$

What is the standard electrode (half-cell) potential? Give its uses.

Amongst the following electrodes,the one with zero electrode potential is